1. Field of the Invention
The present invention relates to an apparatus for detecting gear positions of a manual transmission for a vehicle.
2. Background Art
In recent years, an increasing number of vehicles are equipped with control systems in which a gear position is one of control parameters for controlling fuel injection amounts, fuel injection timing, driving force distribution and the like.
In case of automatic transmission vehicles, a selector position selected by a driver can be detected by an inhibitor switch which is operated by a selector lever, however in case of manual transmission vehicles, a special, independent apparatus is additionally needed for detecting gear positions.
Japanese Patent Application Laid-open No. Toku-Kai-Hei 6-293225 discloses an apparatus for detecting gear positions. In a transmission wherein gears are selected by the combination of a longitudinal motion and a rotational motion of a shift lever, the apparatus comprises three magnets arranged circumferentially on a first rotor, three magnets arranged in the longitudinal (axial) direction, and hall elements corresponding to these magnets arranged circumferentially and longitudinally respectively on a second rotor.
However, this prior art needs six sets of magnets and hall elements in order to detect the respective gear positions of five forward speeds and one reverse speed. Further, wiring arrangements are needed between these hall elements. Therefore, the number of components and the size of the apparatus increase, this resulting in an increase of the man hours for assembling and manufacturing costs.
It is an object of the present invention to provide a gear position detecting apparatus composed of small number of magnets and hall elements, having a small size and of a low cost.
The apparatus comprises a magnetism generating means fixed to a transmission housing for generating a magnetism, a magnetism shielding plate fixed to a rod for selecting a gear of the transmission and provided outside of the magnetism generating means with respect to the rod, for shielding the magnetism, a magnetism passing means provided in the magnetism shielding plate for permitting or forbidding the magnetism to pass therethrough according to a sliding and rotating movement of the rod, a magnetism detecting means fixed to the transmission housing and provided outside of the magnetism shielding plate for detecting the magnetism and for outputting an ON signal when the magnetism is permitted to pass through the magnetism passing means and an OFF signal when the magnetism is forbidden to pass through the magnetism passing means and a gear position judging means for judging the selected gear position based on the combination of the ON and OFF signals.